Technology Of Co-oxidation To Prepare Propylene Oxide From Tert-butyl Hydrogen Peroxide And Propylene

Propylene poxide is an important organic intermediates,which is the third largest derivatives of propylene besides polypropylene and acrylonitrile. Currently, the market demand of propylene poxide in the global is increasing at 5% per year. It is of great broad market prospect. There are two main industrial techniques to manufacture propylene epoxide, which are called chlorohydrin process and co-oxidation method.The traditional chlorohydrin method has mature technology,good selectivity, high yield but in production process it can bring lots of wastewater with chlorine,corrode devices and pollute environment seriously. The technology of co-oxidation has some advantages such as has little pollution , corrosion and high yield of joint products but has long flowsheet,high demand of equipment,high investment cost and can be restricted by the market of joint products.Arco process, the representative of the co-oxidation process, is developed by foreign company. At present, the majority of domestic companies are still using the traditional chlorohydrin process because of the technological barriers and security issues. Therefore, it will be very important to develop environment-friendly production engineering for propylene oxide.This pthesis studies a process of propylene oxide by oxdiating propylene with tert-butyl peroxide (TBHP) as the oxidan, taking the Mo(CO)₆ as the catalyst. Firstly, Mo(CO)₆ is prepared and characterized with ICP-AES and FT-IR. The preliminary evaluation of the catalytic properties of Mo(CO)₆ and other molybdenum homogeneous catalysts has been carried out. The results show that the Mo(CO)₆ catalyst is more effective.A high performance liquid chromatographic method was developed for determination the content of TBHP . Under the optimized chromatographic conditions, each component can be completely separated within 4 minutes. The method showed good linearity with correlation coefficient of 0.9998. The average recoveries rate are between 99.42% and 101.17%. The relative standard deviations for real sample spiked with mixed standard are in the range of 0.36% to 0.52%. The relative standard deviations for reproducibility can reach 0.79%. There is little affect by PH. For its advantages of precise, rapidity,simplicity,economy.It is proved to be a good method to detect TBHP. With Mo(CO)₆ as catalyst, effect of catalyst dosage, reaction temperature, molar ratio of propylene and TBHP, reaction time on epoxy reaction are investigated. Cobalt additive and dehydration is also discussed to optimize the process. The results show that in the condition of Mo Concentration 1.7×10^-4, reaction temperature 120℃, molar ratio 6.5:1, reaction time 1 hour, under anhydrous magnesium sulfate dehydration, the reaction can get a better effect. The conversion of TBHP reachs 82.82% and the selectivity of propylene oxide (relative to TBHP), which is the key target, can reach 91.87%, respectively.In order to discuss catalytic mechanism of this co-oxidation, GC-MS is used for analyze products and deduce the reaction process. The results show that the main by-products in this epoxidation process are 1,2-propanediol and tert-butyl isopropyl ether. The 1,2-propanediol is the product of the side reaction of propylene oxide reacts with H₂O, while the latter forms as a result of propylene oxide reacts with tert-butyl alcohol at high temperatures.